U.S. Pat. No. 4,651,583 describes a locking mechanism. The locking effect is brought about by the action of a spring, which is supported on the stationary bearing of the guide lever arm and holds the pin of the sliding lever arm pressed into the given end position. In accordance with the state of the art, the locking mechanism is swiveled by compressing the spring and causing the pin to slide in the groove until the two lever arms swivel into the other end position, and the spring effect is activated and the end position is thus secured.
A locking mechanism of this type has the disadvantage that, when the swiveling occurs from one end position to the other, force must be continuously applied against the action of the spring. Furthermore the spring is an additional component that complicates a mechanism that is relatively simple in itself.